Defining Hearing Loss

When a baby is diagnosed with hearing loss, there is much to learn. In order to take the next steps and assist with decision making, understanding hearing loss is very beneficial. When describing hearing loss there are three things to consider:

Type of hearing loss

Degree of hearing loss, and

Configuration of the hearing loss

Types of Hearing Loss

There are three types of of hearing loss:

1) Conductive Hearing Loss Conductive hearing loss occurs when sound is not able to go through the outer ear canal to the eardrum and the middle ear properly. This type of hearing loss can often be medically or surgically corrected. Examples of conditions that may cause a conductive hearing loss include:

Impacted earwax

Ear infections

Presence of a foreign body

2) Sensorineural Hearing Loss
Sensorineural hearing loss occurs when there is damage to the inner ear or to the nerve pathways from the inner ear to the brain. Sensorineural hearing loss cannot be medically or surgically corrected. It is a permanent loss.

Sensorineural hearing loss not only involves a reduction in sound level, or ability to hear faint sounds, but also affects speech understanding, or ability to hear clearly.

Sensorineural hearing loss can be caused by some diseases, birth injury, high doses of certain drugs, and genetic/hereditary syndromes. Sensorineural hearing loss may also occur as a result of noise exposure, viruses, head trauma, aging, or tumors.

3) Mixed Hearing Loss
Sometimes a conductive hearing loss occurs in combination of damage in the outer or middle ear and in the inner ear. When this occurs, the hearing loss is referred to as a mixed hearing loss.

Degree of Hearing Loss

Degree of hearing loss refers to the severity of the loss. There are five broad categories that are typically used. The numbers show a measurement of what levels of frequencies can and can not be heard.

Normal range or no hearing loss = 0 dB to 20 dB

Mild loss = 20 dB to40 dB

Moderate loss = 40 dB to 60 dB

Severe loss = 60 dB to 80 dB

Profound loss = 80 dB or more

Configuration of Hearing Loss

The configuration is the measurement of how much hearing is lost at each frequency. For example, a hearing loss that only affects the high frequency sounds would be a high frequency loss and the configuration would show good hearing in the low frequency sounds and poor hearing in the high frequency sounds.

Other definitions associated with hearing loss are:

Bilateral — both ears are affected.

Unilateral — only one ear is affected.

Symmetrical — degree & configuration of hearing loss are same in each ear.

Asymmetrical— degree and/or configuration of the loss is different for each ear.